1. Technical Field
The present invention relates to a force detection device and a robot.
2. Related Art
For example, as a force detection device detecting a received force, a configuration disclosed in JP-A-2015-1384 is known. A force detection device disclosed in JP-A-2015-1384 includes a first base unit, a second base unit, a sensor device interposed between the first and second base units, a pre-compression bolt that connects the first and second base units to each other and pre-compresses the sensor device between the first and second base units, and a circuit substrate (a charge amplifier circuit) that is electrically connected to the sensor device.
A device that deals with a minute signal as in the force detection device disclosed in JP-A-2015-1384 generally includes a signal GND that serves as a reference potential of a circuit and a frame GND that serves as a reference positional of the first and second base units in order to shield disturbance noise. The signal GND and the frame GND are connected via a master GND of low impedance so that disturbance noise flowing in the frame GND does not propagate to the signal GND.
An operation current of a circuit normally flows in a wiring resistor present between the signal GND and the master GND and a contact resistor of a connector, and thus the signal GND has a high potential (for example, about several mV to about tens of mV) with respect to the master GND. On the other hand, a minute current merely flows at a moment at which disturbance noise flows between the frame GND and the master GND, and thus a steady current is almost 0 (zero). Therefore, the frame GND has the same potential as the master GND. In this way, the signal GND has a higher potential as the frame GND, for example. Thus, a leakage current may start flowing steadily in the frame GND from an input wiring of a charge amplifier circuit. Then, since the flowing leakage current is amplified by the charge amplifier circuit and is output, an output voltage of the charge amplifier circuit deviates from an output voltage corresponding to an actually received force (a drift may occur). Therefore, in the force detection device disclosed in JP-A-2015-1384, it is difficult to detect a force with high precision.